A strain-tunable nanoimprint lithography for linear variable photonic crystal filters

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Photonic crystal (PC) filters offer unique optical properties.
• Tunable filters are crucial for advanced optical systems.
• Linear variation in optical properties presents fabrication challenges.

Purpose of the Study:

• To present a fabrication methodology for a linear variable photonic crystal (PC) filter.
• To achieve narrowband reflection that varies linearly over a broad spectral range.
• To demonstrate a novel application of nanoreplica molding for PC fabrication.

Main Methods:

• Fabrication of a polymer surface-relief grating with a linearly varying period using nanoreplica molding.
• Utilizing a wedge-shaped elastomer mold and applying uniaxial force to stretch the mold.
• Determining grating period based on applied force and local mold thickness.
• Depositing a high refractive index dielectric film on the graded-period grating.

Main Results:

• Successfully fabricated a linear variable PC filter with a grating period ranging from 421.8-463.3 nm over 20 mm.
• Achieved a linearly varying resonance reflection feature from 680.2-737.0 nm along the filter's length.
• Demonstrated a tunable narrowband reflection with a broad spectral range.

Conclusions:

• The nanoreplica molding process is effective for fabricating linear variable PC filters.
• The developed filter offers a tunable spectral response over a broad range.
• This technology has potential applications in spectroscopy and optical sensing.